Process for recovering metal values from slags



April 6, 1948. A. M. GRONNINGSAETER PROCESS FOR RECOVERING METAL VALUESFROM SLAGS Filed April 21, 1945 2 sheets-sheet 1A ATTORNEYS April 6,1948. A. M. GRoNNlNGsAETER 2,438,911

PROCESS FOR RECOVERING METAL VALUES FROM SLAGS Filed April 21, 1945 2Sheets-Sheet 2 INVENTOR BY'mv/v/,vafdfrm l I, 4 E l ATTORNEYS PatentedApr. 6,1948

naiven sT-AT Y rnocnss ronREcovERrNG METAL VALUES FROM sinds AntonMartin Gronningsaeter, New York, N. Y., i assigner to FalconbridgeNickel Mines, Limited,

Toronto, Canada Ontario, Canada, a corporation of Application April 21,1945, serial No. 589,674

as nickel and copper. 'Ihez` inventionhrelates f more particularly toimprovements in the treatment of slags obtained inthesmelting of metalores, such as nickel and `copper ores, to recover a substantial amountof their metal values.`

There are at present` two conventional methods p of smelting nickel andcopperoresV in which `the essen-tial metals, nickel and copper, as.Well' as a substantialamount of iron, are present as suldes. Each ofthese methods results :inltheproduction `of mattes andslags; andincludes a procedure for treating the slags to recover` as much of theirnickel and copper-content as. possible under the circumstances. i ;x

According toone `of said-` methods,` knoWnfas the blast furnacepractice, a charge of suitably ,Y

prepared nickel `ore issmeltedlinx ablast furnace. Thecharge.ccnsists,ifor example, of unroasted ore, sintered flotationconcentrates and ue dust, converterA slag,` limestone and .'coke.

The smelting results inthe production of ar lowgrade matte and a slag.The'fluid slagand matte are run into a settling vessel, known as a.settler. The blast` furnace matte contains, for example, iron, copper,lnickel, cobalt and gsulfur. s This low-grade matte `isthen transferredto a converter where it is :blown with Iairuntil the. iron is oxidizedand fluxed, and; passes almostcome f pletely` into the resulting`converter slag, leaving a high-grade converter matte vconsistingmostlyof nickel, copper and sulfur, with very little iron.

The converter slag contains, an `appreciable amount of matte prillsandhencevaluable nickel and copper, whichffailto settle and mergewith thematte. t also contains copper,"nicke1,` and most of the cobalt` ascxidesand silicates; and

Ametal sulfidcs insolution.` Aportion ofthe cone verter slag is in someinstances chilled 'and-used as a basic flux in the blast furnace,whilethe remainder of the liquid converterslagis` poured 2 istransferred to the con- The resulting reverberatory slag is dis-`tleout, and the `matte verter.` carded.

These two main methods of smelting nickel oresmay,.o`f course7 be variedin operating detaili An effort is made in both methods to recover asmuch as possible of the valuable nickel and copper which find their wayinto the slag. A typical converterslag maycontan from 1 to v5% ofnickel.. pluscopper, and vit istherefore economically inadvisable todiscard the slag without recovering at least some of the nickel andcopper. ,l

The presence of nickel and copper in 'the `converter slag is due partlyto mechanical and partly tobchemical causes. The slagcontains some matteprills in suspension. Failure of the matte prills tosettlemaybe duein'large part to lack of time beforeskimming .the slag from the `con--verter.V :If sufficient time `weretaken to permit more complete settlingout of the prills, too much of theair-blowing time vof theconverterwould befwasted. Converter slags have a hghllspecic gravity-on accountof their high iron content, which tends to` retard the settling rate ofthe prius', Yas probably does the high content of magnetite. l `Chemicallosses in the converter slag appear to `be due to a numberrof causes.Amongthese is the solution of suldes lof copper, nickel, cobalt andironiny slag silicates; `'It is 'believed that the copper sulde isrelatively more soluble Athan the nickel sulfide. While the solubilityoithese metal, sulfldesA in the slag silicates appears to bemore`greatly affected by iron silicate, other silicates .present Vin theslaglikewise` appear to have ysome effect thereon. The factor ofdifferences A:of solubility of such metal suldes, including ironsulfide, in slags Vof. different composition into the settler, whereitisimperfectly mixed with the blast furnace slag; and apartialcleaningtakesplace .while matteprills settle toxthe bottom. The slag portiontofthe mixture iisdiscarded, and the matteis treated inthe converter.v

Substantially the same procedure is followed in f the other4conventional method` of -smelting nickel ores, known asthereverberatory vfurnaceprac-` i is transferred while still liquid tothe reverberatory where it is imperfectlyl mixed Witht the slag of theregular charge; the matte prills set- The reverberatory matte is'thenthough this solubility` is `not indirect proportion 'to the` iron*content ofthe slag but increases more rapldlygthan the iron contentdoes. This may be illustrated by suchvdata as the` following:

, Fe SOzV A1203 'S Converter Slag 57. 2 12. 5 4. 0 4. 6 Converter Slag52.2 l18. 23 3 6 Blast Furnace Slag. 37.1 "36. 9 8. 50 1. 57 BlastFurnace Slag. 28. 6 35. 4 11. 90 1.14 Blast Furnace Slag 28. 2 l 36. 51B. 00 `0. 70

The figures given are in percentages. It will be noted that as theamount` of iron, Fe, increases, the `amountTofsulfur.,:S,-:increases atan acceler- ,K ated rate; :The amount of sulfur, ofcourse, indicates theamount of metal suldes present in the 3 slags. The result is that whentwo slags of different iron content and hencediiferent solubilitycharacteristics for metal suldes are mixed, the total solubility ofmetal suliides in the mixed slag is less than the sum of the solubilityof the metalV sulfdes of the two components and metalsulfides aretherefore salted out of the slag byjthemix.. ing. The chemical losses inthe converter slag also appear to be due in part tolthe formationrfoxides or silicates of nickel/andcopperfas l-wel-l' as the oxide andsilicate of cobalt if' it is desired to recover the cobalt, particularlyin the nnishing period of blowing the matte with air. Chemical losses inthe converter slag in the third place also appear to be due to thepresence inthesslag of iron in the form of magnetite, which appears tocarry a lconsiderable amountof the nickeland copper combined eitherchemically ormechanically.

The converter slag may be substantially freed of nickel and copper bycooling; breaking up the solidiied slag and resmelting it with :thenickel ore in the blast furnace, `as indicated above By such resmelting,the matte prills are given an opportunity to settle inthe normal Way ina slag of normal temperature, viscosity and specific gravity. The brokenup converter slag is mixed Withthe slag from the ore charge, and by thismixing the suldes in the original converter slag are salted out to thepoint'that corresponds to their regular solubility in aslag of thecomposition of the blast furnace slag. ,Oxides andsilicates of nickeland copper are at least to a Very substantial amount again reduced and,in .thepresence of iron sulfide, regardless of what the intermediatereactions may be, end up as copper-nickel suldes. It is believed thatthe reduction isfairly complete for copper and nickel but not forcobalt, usually present in nickelbearing ores. Magnetite is soluble iniron sulfide to a considerable extent and a considerable part `of themagnetite presentjnthe -converter slag goes into the matte. Asubstantial amount of magnetite goes into the final slag. In the vblastfurnace, butnot to the same extent in the reverberatory furnace, themagnetite is partly reduced so in mostcases theremaining amount isperhaps in proper solution in the slag, and the combination betweenmagnetite, nickelfand copper` is perhaps at the same time broken up, Theindications therefore are that by resmelting the converter slag in theblast furnace, the recovery of nickel and copper from the slag iscarried about as far as it can be under the circumstances for a nal slagof given composition.

On the other hand, when converter slagisreturned while still in liquidform to thesettler or to the reverberatory furnace, conditionsaresubstantially different. In the settler there is the disadvantage ofsomewhat lower slag temperature, which tends to inhibit the settling outof matte prills. In both the blast furnace settler and the reverberatoryfurnace, conditions are such that the silicates and oxides of Vnickeland copper and magnetite vcarrying valuable metals are likely to passthrough more'or less unchanged. This appears to be due to the fact thatthere is insufficient opportunity for these compounds to be reduced ordissolved in matte and to the further fact that there is insuiiicientopportunity for thoroughly mixing the liquid converter-slag with theblast-furnace slag or the reverber'atory furnace slag proper so that the-mixturesmay be conditioned to make possible the salting out of some ofthe dissolved suldes. I n addition, considerable variation in escapingslag composition ,is caused ,byiunavoidable irregula-rvreturn of liq-:uidconverter `slag to the reverberatory furnace or settler. It is wellrecognized that the return eo'f the liquid converter slag to settlers orto re- .verberatory furnaces will appreciably increase theslagllosses."However, the increase is generally not su'icient to justify cooling,breaking up sand-resmelting of: any more of the converter slagrthanfisrequiredasa flux.

IExperienceshows that the slag losses in reverberatory smelting Aareeven higher than the slag ilossesfin-blast yfurnace smelting, with slagsof similar composition; presumably because reduc- 'ingconditions in thereverberatory furnace are not as good as those in the blast furnace. Theslag :losses .in the reverberatory furnace are, 4ther.efore,;increasedon .account of larger-l amounts zofuoxides'and silicates, andthepresence of more lmagnetiteawhic'h is'fgenerally also formed by theroasting ofrthe orebefore it is charged into the reverberatory :furnace`.besides being introduced from the liquidfconverterslag. Slag losses inreverberatory yfurnaces are often increased be- :cause y,of`irregularities in operation, when unsmelted for :insufficiently heatedmaterial still .containing suldes :is `entrained by and moved out-withsthe slag, The average slag losses from reverberatory "furnacesmelting are, therefore, probably almost alwaysappreciably higher than,is lindicated by 'asample of lthe vnormal slag.

'.In the `productionfof copper, as distinguished from nickel, thepractice-'is similar; vand what has :been :said specifically.Withrespectlto nickel also holdsatrue, at least forthe mostrpart, forcopper.

lIt will the; clear f that :present smelting practice leaves muchto bedesired with respect to nickel and copper` -lossesf in. ther finalslags.

Various methods have 'been proposedto treat l copper-bearing-slagstorecovertheir copper conrtent,; at 4leastinsubstantial amount, apartfrom .the conventional practice of l. chilling and returningsa. portionofsthe converter vslag as flux toa blast furnaceiand ipassing the:remainder of ythe converter-slag to a: settler, and of :returning themoltenconverter.slagttola reverberatory furnace, such -assjustdescribed. Practically 1 all investigations have :been directed .towardthe. cleaningY of converter. slagsfalone, withrthe View of discardingthe final slagfreed o'f the. desiredmetals.

One `early investigatorpfor example, subjected Ia,bath.oflconverterislagto a reduction operation totreleaser: and settle out th'ecopper. =Tothis end, he `placed ifineicoke onthe 'bath and stirred themolten-slagvwithfa .green pole :to mix the coke thoroughly into theslag. lI-I-e operated under the theory thatthecopper ispresent in theslag as -coppertsuli'i'deythat the slag is charged-withmagneticoxideiofiironpthatI the copper sulfide' is dissolved inthemagneticioxideof iron; that the reductionf-steprcauses the fmagneticoxide of Viron toreleaseithe copper and'that-the-released copperthenfsettles out. Oper-atingfwithconverter slags containing 2l1/2% lcopper,he-foundthat the copper contentV in lthe `'slags could beAreduced fto 01346217 %.A This method leaves toofvmuch valuable copperin the slag in-view of=the inconvenience and costltopractice it,so thatthe proposal has not attainediany commercial success. It was abandoned.

rinstead:oivstirring` the reducing agent into the bath vofaconvei-terslagfother investigators later proposedrtoi'inject thereducing agent,*such as pulverized `coal, through -the bath, preferably through .fabathaf slag -in contact with matte.

l They operated under" the theory that copper is present in the slag ascopper oxide; that the' slag contains magnetite, Fe304`; vthatthemagnetite holds the copperin solution 'or in suspension; that thereduction step causes the-magnetite to release the copper; and that the'released copper ythen settles out. The reduction operation is conducteduntil an 'appreciable amount of the iron oxide in the slag is'reduced tometallic iron and the metallic iron is dissolved in the matte to give aslag of higher silicate'degree and of lower specic gravity, so that'theslag holds less copper matte in solution or suspension.` The work ofthese investigators appears to have been confined almost `exclusively toth'e treatment of converter slags, although they indicate thepossibility of treating blast and' reverberatory slags. 'Ihe methodproposed has notbeen used commercially. My experimental investigationshave confirmed my discovery that if the slags are properly treated, asubstantial amountof their metallic values may be economicallyrecovered. -This is particularly true of blast furnace or reverberatoryfurnace -slags containing valuable amounts of such metalsas copper,nickel and cobalt. To obtain these long sought-for results, a workablehypothesis or theory of the nature and characteristics of the slagsappears necessary, so that the method of treating the slags may bevaried accordingly. Those `engaged in this industry appreciate that thebest present knowledge of` such' slags -is imperfect and certainly notexact in all particulars. While our supposed `knowledge may beincomplete and theoretical, at least in part, it does seem true thatpractical methods of treatment are seldom based on fallacious theories;they are usually based on `a fairly accurate .appraisal of what takesplace. I am convinced that methods proposed by prior investigators, suchas those referred to, failed because they are unsuited economically andmetallurgically for slags ofthe composition actually treated. l l

'Ihe above-mentioned attempts to cleanconverter slag alone have not beencommercially successful, apparently dueto a lack of appreciation of themetal sulde solubility conditions in such slags. The converter slag hastoo highan iron content and too high a metal sulfide solubility to makeit` possible regularly to lower the coppernickel content of the slagsufficiently to discard it directly without going to the extreme step ofreducingout metallic iron and-thereby lowering the metal suldesolubility in the lremaining slag. It is neces-sary to obtain a nal slaglower in iron than the converter slag, and therefore of lowermetalsuliide solubility. By specially mixing the high iron converter slagwith a lower iron slag, so to say using the ore slag as a flux, it ispossible .to get a metal sulfide salting out action. That is, sulfidesof copper,lnickel,icobalt and iron may be thrown out `of solution in theiron silicate. i Imperfectly mixed but partly cleaned slag from areverberatory furnace or a blast furnace settler are passed through areducer-mixer vessel while blowing in coal, or other reducing agent. Ihave found that by takingadvantage of the selective reduction of theseries copper-nickelcobalt-iron oxides, I can so regulate reduction ofthe liquid slags that substantially all, or most of the very smallamounts, of the copper and nickel oxides and silicates in the slags arereduced and converted to their suldes in the presence of" iron suldes,by y a comparatively short treatment Without reducing much' of the`oxide and silicate of cobalt or an appreciable amount of the ironAoxides. I have further found that by passing the slag mixture, alreadypartly cleaned, continuouslyand'relatively quickly through areducermixer, and regulating the amount of fuel for reduction, thetemperature and the time of slag mixture staying in the reducer-mixervessel, I can obtain substantially the selective reduction I am aimingfor at the same time as I obtain th'e desired mixing and lsalting ou ofmetal sulfides. It appears that the small and VWell distributedparticles of salted out iron sulfide function to convert the reducednickel and copper to their suldes. Y

Previous investigators seem to have paid major attention to thereduction of magnetite,l

which needs a prolonged and expensive treatment. My investigationsindicate that such substantial reduction of magnetite is not necessaryand that nickel and copper oxides and silicates are substantiallyreduced before a substantial reduction `of magnetite takes place. Evenif a certain amount of nickel and copper is `connected or tied up withmagnetite in the converter slag, this is substantially overcome in myway of operation, first by returning the converter slag toareverberatory furnace or to a settlerwhere a large part of the magnetiteis dissolved in the iron sulfide in the low-grade matte, and next theremaining magnetite is diluted by the ore slag to such a low percentagethat it, by the mixing operation, probably goes into the slag dissolved,or otherwise, in such form that it retains no appreciable amount ofnickel and copper. The 10W- ering of magnettein the final slag indicatedin my experiments may be due in part to solution of the magnetite in theiron sulfide in the matte prills present in the slag entering thereducermixer and due in part to solution in the salted out suldes,although it may also be due in small part to reduction.

The economy of the method can, besides the salting out principle, besaid to depend upon selective reduction. The aim is to reduce onlycopper and` nickel oxides and silicates, not cobalt and iron compounds,in case the cobalt is to be excluded. As the slags have already beenpartly cleaned in the reverberatory or settlers, comparatively littlereduction is needed, and it is found that the reduction obtained bypassing the slags `continuously and relatively quickly through areducer-mixer is sufficient. It is only a question of reducing fractionsof 1% of copper-"and nickel compounds. In present reverberatorypractice, as noted above, slag losses in reverberatory furnaces areoften increased becausevof irregularities in operation, when unsmeltedor insuiliciently heated material still containing metal sulfides isentrained by and moved out with the slag. The average slag losses fromreverberatory furnace smelting are therefore probably almost alwaysappreciably higher than is indicated by a sample of the normal slag.When using my method, these unsmelted or semi-smelted suldes are smeltedin the `reducermixer, the slag llosses are lowered correspondingly andan analysis of the final slag gives a reasonably correct picture of whathas taken place.

One advantage of the method is thatslags of higher iron content will bepractical, permitting more flexibility in operations. In copper andnickel smelting there is generally a limit to the iron content in thefinal slag, above which `the metal losses increase to apointconsidereduneconomical. While higher iron content in the slugsincreases metal losses also when using my process, duo to higher metalsulfide solubility. the difference is .not so large. some cases .it Willbe economical. to aim as .a regular practice .for a somewhat higher ironin the slags than before and any accidental extra high. iron will not beso lserious as before. The reducer-.mixer aets. as a "ilywheel to.y evenout variations .or iron in the slag .flue to the irregularities in thereturn of lig.- uiel yoiuuyerter slag or to other 1 .It is thereforeurl-neoessaiy to regulate slr1..t.iiig oonclitious in reverheratoryA andblast iurriaoes as carefully as heretoforegbeoause the irregularitiesmay be corrected in the reducer-mixer. This permits' more4 flexibilityin smelting Operations with increased economy. The process also permitsgreater flexibility in the choice of both converter and reverberatoryslags and therefore the lowering of they quantities of fluxes needed'and morefvariations in their composition.; the process permits the useof a lower grade of concentrate with correspondingly lov/er tailinglosses. This increased flexibility in meeting existing vcomlitions ishighly important economically,

The alcove-described operation of the process is primarily for therecovery of copper and nickel but not of cobalt. However, I have furtherfound that by more intensive reduction, more coal or more time or' ahigher temperature vor a combination of all, I can reduce most of thecobalt and collect it in a matte either in the same operation thatrecovers copper and nickel, or in a separate operation that follows thetreatment for copper nickel recovery. For cobalt recovery, batchtreatment and as intensive mixing as possible -with a large excess ofiron sulfide appear advantageous.

These and other features of the invention will be better understood byreferring tothe accompanying' drawing, taken in conjunction with thefollowing description, in which- Fig. 1 is a diagrammatic representationof apparatus illustrative of the invention, which is adapted forblast'furnace practice;

Fig. 2 shows a modified form of the apparatus adapted for reverberatoryfurnace practice;

Fig. 3 is' a plan View o f a reducer-mixer associated with a settler,which may be used oorliunotion with the apparatus of the above figures;and

4 is an elevation in section of the arrangement shown in Fig. 3.

Referring iirst to Fig. 1, the apparatus .shown comprises a smeltlugfurnace iu the .form of a blast furnace lll. a sett1er I l, areducer-,mixer l2.. a second settler I3, and a converter I4. A matte.-slag yconduit vIll connects the blast furnace with the settler; a `slagconduit It connects the rst settler with .the .reducer-mixer; andaslag-.matte conduit ll connects the reducer-mixer with the secondsettler. The second .settler is provided with .a matte .discharge IB.and a .slag .discharge L9. Means, not shown, are provided fortrailsierring liguid slag from the converter to the set.- tler, as wellas solid slag to the ,blast furnace, if desired, and matte from thefirst settler to .the converter.

The reducer-mixer may be patterned after the conventional converter, or.slag furning furnace and is .provided with a plurality of nozzles 2l),adapted for the passage therethrough .of ,air ad, mixed with fuel intothe reducer-mixer; conventional means 2| for mixing the ,air and fueland injecting the same into the reducer-mixer; ,an

extra discharge 22; and .au not shown, Afor the essere of leises` iReferring next to Fig. .2.. the: apparatus .is essentially the .same as.lust described. eurent that the .smeltiug furnace is the .ferruol auaoo ltwitli-means. .not ,for transierrin. matte from the reverlleratoryis the couvertes. and slag .from the converter to the reyerberatory .A.slag eouduit .3l connette the reverberatory with the reducer-mixer 3l,while a gas conduit 32 Yconnects the realiser-mixer with .a rooster 33which ln tum oom uuioates with the .reyerloeratory furnace by means of aconnes een 34.

Referring, zflrially,V te Elles. 3 fl. the appafetus shown is .a.somewhat more detailed arrangement of u .resister-.miser l2... withshriek lining 3.5. ausl settler la., with a brisk lining :3.6, which wasemployed in my exreriments. to be disoussecl below.. .In theconstruction illustrated, slag charging seriell-lit LS is inclineddownwardly lute the interior of eueeufl o f the reducer-mixer.preferably term/rating slightly above its .normal slag. level 3l.. Aplurality or nozzles or tuyres .20 sonnent with the interior .oftheslagseharging portion of the reeluoerfmixer'. preferably well wit. .inthe .slag zone, .as shown. v.that is.'

3:8 below the tuyeres and .a relativelyquieseent Y Zoll@ 4l] beyond thetuyeres toward: the opposite or -slagaaeg-g,tte discharging end of thererincer-mixer, @houd of settler i3, An opening or vent .4l is providedin the top of the reduceramixer, pref.- eraloly near the discharging.end of ythe reducer,- 'iiiflen for the escape .of gases. Slag conduit Hconnects with anoutlet .42 at the bottom of `the dlShaIgl-ng emlofthe'reduc-.er.-mixer.v This con.- .d-uit is advantageously lin theforni. of an ,open tran-trough@ trap-espout, shaped as shown.v vThe.bottom .of the trough .is inclined upwardly and the side Walls of thetrough are parallel to one another, extending .a vsuit-.able distanceabove outlet 42.- AS t0 bey .explained in more .detail loe-- low. thetrough is so loi-'oportionedy as to permit passage therethrough .ofmatte and. slag from the reducer-.mixer to the settler to maintain allbstantially constant slag level within the re.- duoer-mixer. Thedischarge en d .0f .theitrough extends over the top of the settler, sothat matte .and slag passing through :the trough Vmay fall within. theinterior of the settler. Conduit I8 located at the bottom of the settlerfor the dis;- .charge .of matte .and conduit I9 is vlocated at ahlgherleuel fortherl-ischarge of `final slag.

The apparatus of Fig.. l may be .operated as follows:

Nickel ore is .charged into blast furnace lll, Where git undergoesinitial -sme-lting. The result.- ing mixture .of matte and slag is.conducted sub.- .stantially continuously through yconduit l5 into rstsettler l'l. Matte is withdrawn from .the .settler and transferred toconverter L4, l,wlfiere lit is .blown with air in the usual `marmer toremove objectionable iron present therein. Highegrade nickel matte isformed and withdrawn as such from the conyerter. The resultingeonyerterslag maybe advantageously .withdrawnin part, chilled and brokenup. ailier which it is `introduced into the blast `furnace charge tofunction essentially as oasis illu: ...-aterial.

The rom oder oi the sortierter slag. orali of converter slag. .as the.ses may be, inasse@ iu liquid llortu :into iirst settler Ll, Where .itis @unlisted with .slag .and matte eomlug i.from the 9 blast furnace;and the combined slags are passed through conduit I6 into reducer-mixerI2. Due to the agitation caused by the introduction of air and fuel intothe reducer-mixer, the slags are l intimately admixed above relativelyquiescent zone 39 (see Fig. 4), which causes some of the nickel andcopper `suliides present in the converter slag to salt out, at the sametime as the slags are exposed to selective reducing conditions in thepresence of iron sulfide. Matte prills settle and form a layer of matteat the bottom of the reducer-mixer, in zones 39 and 40, as shown in Fig.4. Slag and matte are withdrawn from the reducer-mixer through conduitI'I into second settler I3. The slag is permitted to remainsubstantially quiescent so that additional matte prills may settle bygravity to the bottom to merge with matte forming thereon. The settlermatte is withdrawn through discharge I8, while the final slag iswithdrawn through discharge I9 and discarded.

Substantially the same procedure is followed when smelting copper oresin accordance with the blast furnace practice. In such cases blisterycopper is of course withdrawn from the converter.

The apparatus shown in Fig. 2 may be operated as follows:

Nickel ore is fed into reverberatory furnace 30 in the usual manner, forexample, from roaster 33 through connection 34. The resulting matte istransferred to converter I4, Where it is blown with air to eliminateobjectionable iron. Highgrade nickel matte is formed and withdrawn fromthe converter. The resulting converterl slag is transferred to thereverberatory furnace While still liquid, where it merges with thereverberatory slag proper, and where it is freed of nickel and copper tosome extent. The admixed slags are conducted substantially continuously,the flow of slag being interrupted only while matte is tapped into theconverter, into reducer-mixer I2. l-lere the slags are subjected, in the`presence of iron sulfide, to the reducing and mixing action of air andfuel introduced through nozzles 20. This operation is described morefully below in the case of Figs. 3 and 4. The resulting slag and matteare withdrawn through conduit I'I into settler I3. Matte is withdrawnthrough discharge I8 While the final slag is withdrawn through dischargeI9 and discarded.` Gaseous products of combustion formed in thereducer-mixer may be conducted through conduit 32 into roaster 33, wheretheir heat is effectively utilized to roast ores about to be charged tothe reverberatory furnace through connection 34, or the hot gases may beotherwise utilized.

In the production of copper, substantially the same practice isfollowed. The copper ore is initially smelted in the reverberatoryfurnace. The resulting matte is conducted tothe converter where it isblown with air to form blister copper; while the converter slag isreturned to the reverberatory furnace to be admixed with thereverberatory slag. The admixed slags are then conducted to thereducer-mixer where they are subjected to reduction and mixing. The slagand matte are withdrawn from the reducermixer and are flowed into thesettler. Matte prills settle to the bottom, from which the resultingmatte is withdrawn. The settler slag is passed thro-ugh its dischargeand is discarded.

These features of the invention may 'be better understood by referringto the manner in which` the more detailed apparatus of Figs. 3 and 4 maybe operated. The slags are passed through conduit I6 or `3l intoreducer-mixer I2 until slag level 31 is reached. Fuel and air are passedthrough nozzles or tuyres 20 into the body of slags, rather than thebody of matte which tends to collect -at the bottom of thereducer-mixer. This arrangement permits the use of a smaller settler,although this is not normally necessary. As noted above, the nozzlesortuyres are located toward the charging portion of the reducermixer. Asa result of this arrangement, agita'- tion or mixingof the slag isprimarily confined to the charging portion of the reducer-mixer abovethe nozzles or tuyres, so that slag below the nozzles or tuyres and inthe discharging por-l tion of the reducer-mixer may .be in a relativelyquiescent condition, thus facilitating settlingV out of matte prills andmerging thereof with matte at the lbottom` of the reducer-mixer. Theamounts and rate of fuel and air passed into, and the rate of passingthe slags through the reducer-mixer are regulated to insure the desiredreducing and mixing conditions. The amount of reducing agent and thetemperature of the slag may thus be adjusted to a point at which thedesired selective reducing action or actions take place.

As further amounts of slag are passed through conduit I6 into thecharging end of the reducermixer, matte and slag are passed from thereducer-mixer through outlet 42 at the discharging end ofthereducer-mixer. Conduit Il, as point,- ed out above, is designed as atrap-trough or trap-spout to permit passage of matte and slagtherethrough to settler I3 at a rate to maintain the slag in thereducer-mixer aprpoximately at its normal level 3l. As the amount ofslag in the reducer-mixer rises i in level, a point is reached at whichits weight is sufficient to force matte as well as slag through outlet42, and hence through conduit or trough Il. In this manner, slag may becontinuously passed into the reducer-mixer and treated slag and mattemay be continuously passed out of the reducer-mixer.

Hot gases formed in the reducer-mixer as a result of the combustion ofthe fuel and air are passed through opening 4I in the top ofthereducer-mixer near the discharging end. The hot gases may beexhausted to the open atmosphere or passed through a conduit connectingthe opening to some other place for use. As shown in Fig. 2, forexample, the hot gases may be passed through conduit 32to roaster 33.

Matte and slag passing through conduit o trough I'I are dropped intosettler I3, where the mixture isV permitted to remain substantiallyquiescent. Matte prills settle out and merge with matte forming at thebottom of the settler. Since` slags are continuously passed through there-V ducer-mixer, slag and matte may be continuously passed to thesettler.

In a presently-preferred practice, finely pulverized coal is blown'intothe slag bath. in the` reducer-mixer withV air, the relative amounts ofair and coal being so regulated as to establish reducing conditions inand over the slag bath. The amount of air and coal is also preferablyregulated in conjunction with the rate of speed with which the slags aretreated to provide and maintain a predetermined desirable temperature inthe slag bath; and, if desired, to raise the temperature of the slagbath to a point which assists the reduction and at which the settlingout of matte prills may be facilitated when the slag is passed into thesettler. The desired tem- 1l 'perature may of course be obtained in `anyother suitablemanner.

Thisoperation will eieet a very good mixing tof the slags within thereducer-mixer 'and this, in turn, facilitates the salting Iout of thenickel land copper sullides to a point that Ycorresponds to thesolubility of suliides `in the -1'inal mixed slag. The reducingconditions established in the presence of iron sulde to Va large extentvreduce oxides and silicates of nickel and copper and v convert them tosuldes. Ordinarily, there will vbe enoughiron sulfide present in theslag to effect this highly desirable result. If not, it is advantageousto introduce special liquid Vmatte containing the requisite iron suliideor solid iron s'uli'de containing lore in to the reducer-mixer.v

In the production of such metals as nickel and copper, at least twodilerent .slags are produced, one inV a blast furnace or in .areverberatory furnace, Whichever is employed, and one in a converter. Inthe practice of the present invention, one slag is used to clean theother slag, lhje slags have differing 'speci'c gravitie's and differingsolubility characteristics for metal sullid'es normally present in thes'lags. 'The coverter slag is relatively high iron, low in silica, ofhigher specific gravity, and has a hgiher sol= ubility characteristicfor metal suldfe's, while the blast furnace slag or reverberatoryfurnace slag, on the other hand, is lower in ilon, higher in silica., oflower speciic gravity,'a`nd has a lower Solubility characteristic formetal sulfldes. The slags are passed while still liquid `into the mixingand reducing zone of the reducer=mixei3 and subjected to mixing andreduction -in the presence of iron sulde at an appropriate elevatedtemperature. Due to the intimate admixing of the two slags, the'solubility characteristics 'of the slags for metal suldes are changed.The solubility characteristic oif the converter slag is lowered, so thata substantial amount of its metal sultides is salted out.

The mixing step also functions to average the specific 4gravities of theslags. That of the con'- verter slag is normally so high as to, retardthe setting of matte prills. As a 'result of the inti-inate mixing ofthe two slags, the disadvantage of the higher specific .gravity or theconverter slag is substantially lessened, and settling vconditions formatte prills 'are materially improved. The slag resulting from thereduction and mixing operation is lpermitted to settle, after which ytheresulting matte and iinal slag Aare separated.

The amount of heat required to conduct 'the mixing and reducing`operation in the reducermixer is relatively small, and need not be ex=cessively high. The heat valve contained in the reduc-ing gases escapingfrom the reducer=mi`xer may be utilized for some useful heatingpurposes, and the cost of the coal used in the reducer=mixer maytherefore be divided between two or more operations. This is veryimportant,- since the gaseous products of reduction escaping ,from thereducer-mixer may contain from two-thirds to three-fourths or even moreof the heat value of the fuel in a form that Vmay be convenientlyutilized for drying; preheating and roasting of the ore about to becharged into the smeltingfu'rn'ace, for firing of a reverberatoryfurnace, or for other heating purposes, such as making steam, etc. Eventhe use of a large amount of fuel in the reducermixer may be justifiedbecause .part of the cost niay be charged to other useful and necessaryoperations. If the slag to be treated contains an appreciable Vamount ofcobalt, a pro'- 12 longed treatment ofthe slag under reducingconditionswill remove a considerable amount ofthe cobalt from the slag and therebyeffect a considerablev concentration of the same in the matte.

In order to obtain the desired results economically, it is 'highlyimportant to provide and maintain practically uniform operatingconditions. To this end, in the presently preferred practice of thepresent invention, the slag is fed practically continuously into thereducer-mixer. In the blast furnace practice, the blast furnace slag is-f'ed continuously into the settler, where it is admixed with theconverter slag, and theA combined slag's are then passed into thereducermixer. In the reverberatory furnace practice, the combinedreverberatory and converter slags coming from .the furnace are fedcontinuously into the reducer-mixer.

The substantially continuous feeding of slag to the reducer-mixer `hasimportant advantages. When the optimum conditions have been establishedthat are .practical under the circumstances, in regard to mixing andsalting out of the suldes, the reduction of Ioxides and silicates inthepresence of iron sulfide, and the slag temperature and slag'viscosity favorable to the operations, it is comparatively easy tomaintain and fairly close-ly control such optimum conditions. At thesame time, this accurate control under such `coniditions is possible`-with a minimum of labor and attendance, a minimum of fuel and aminimum of Awear and tear on the equipment. The whole treatment becomescomparatively cheap compared to what a batch process would cost, and itshould not, therefore, take much saving to justify the treatment. Thecontinuous operation i's therefore preferred. But there may be caseswhere Vit Vis economically advantageous to use the more costly batchoperation, for example, in the recovery of cobalt.

Nickel sulde ores 'subjected to present conventional 'smeltingoperations generally contain cobalt in the Iratio of about 3-6 parts toabout 100 parts nickel. Asa result of the treatment of the smelter mattein the converter, Va great deal of the cobalt, for example 60 to 90%, ispassed into the slag. The cobalt may then be present in the nal slag,Which has heretofore Vbeen discarded, in the ratio, for instance, ofabout 50 parts to about parts of nickel. In other words, the slagmaycontainone-half or vmore Vas much cobalt as nickel. An importantadvantage of the present invention may lie in the treatment of such slagin the reducer-mixer to recover the cobalt. By prolonging the treatment,conducted as far as economic conditions justify, Va considerable part ofthe cobalt is' reduced and collected in a small amount ofcopper-'nickel-cobalt matte.

In the smelting of nickel-copper ores containing a valuable amount ofcobalt, the slags may be treated in accordance with the inventionselectively to recover the copper-nickel, or the coppernickel-cobalt. Inaddition, if itis desired to-recover a substantial amount of the cobaltseparately, it is advantageous to proceed as described above in orderselectively to recover the coppernickel, leaving the cobalt in the slag.This cobaltcontaining slag is then separately treated in a reduceremixerin order to throw the cobalt-out of the slag. To this end, sufficientfuel and air are injected into the slag to raise it to the temper'atureat which the oxide and silicate of cobalt are reduced. To insureconversion of the reduced cobalt to cobalt sulde, a suitable amount ifiron sulfide is caused to be present in the slag. This is advantageouslyaccomplished by feeding iron sulfide into the reducer-mixer.

While the cobalt-containing slag, substantially lowered in copper andnickel, may be treated in a reducer-mixer, such as that described above,1 prefer to use one of the converter type which may be tilted fromposition to position during successive stages of the operation. Thus,the reducer-mixer may be tilted at an`angle to permit a batch of theslag to be admitted therein while the tuyres are above the normal slaglevel. As the fuel and air are injected, the reducer-mixer is tilted tolocate the tuyres at or near the bottom thereof, so that matte tendingto collect at the bottom is intimately admixed with the slag. Thereducing-mixing action is conducted until the oxide and silicate ofcobalt are reduced and converted to cobalt sulde by the iron sulfidepresent in the slag; the reducer-mixer is then tilted to bring thetuyres above the slag level; after which the mixture is permitted tosettle while still in the reducer-mixer. 'I'he reducer-mixer is nexttilted more and more as the top layer of slag is withdrawn and then thelower layer of matte containing the desired cobalt.

The practice of the invention may be considered in conjunction with thespecific treatment of slags obtained in the smelting of nickel-copperores in a blast furnace, the method of obtaining the slags being thatdescribed above and illustrated in Fig. 1. The slags were passed whilemolten from a first settler Il to and through a reducer-mixer l2 andthen to and through a second settler I3, such aus illustrated in Figs. 3and 4. Although the experiments were conducted on a pilot plant scale,the operating conditions were somewhat irregular, as is usual in suchcases. On a commercial scale, the operating conditions would, of course,be more regular. In thefollowing table, data is set forth in percentageson typical examples of results obtained in the treatment of such slags.It will be noted that in each of the six (6) examples, data is setforthto indicate the composition of the slag as it went into thereducer-mixer, as well as the composition of the slag as it went out ofthe second settler.

It will be noted that there are some gaps in the Cu Ni Co SiO: Fe F304 SSlag into reducermxer 0.195 0.236 31.60 34.05 5.25 1.41 Slag outfSett1er. 0.13 0.106 31.20 34. 50 4.91 1.10

Slag into reducermixel 0.262 0.411 0.153 30.50 34. 20 5.43 1.71 Slag outolsettler 0.116 0.101 0.120 31.70 34.45 3.58 1.05

Slag into reducermixel' 0.117 32.10 37.50 Slag out olsettlern... 0.1120.068 0.084 31.66 38.10

Slag into reducermxer 0.15 30.60 36.33 3.41 1.56 Slagout oisettler.--0.105 0.071 31.24 37.05 3.10 1.43

Slag into reducermixer 0.173 0.218 28. 38.50 5. 26 1.73 Slag Outofsettlen.-. 0.132 0.088 29. 44 38.00 4.22 1.47

Slag into reducermixcr 0.185 0.268 0.123 29.14 37.92 4.53 1.78 Slag outof settler.- 0.111 0.073 0.099 29.04 37. 4.00 1. 44

Referring to the S, sulfur, column, it will be noted that there is anappreciable drop in each 14 of the examples. This clearly demonstratesthe salting out of metal suliides. Referring next to the FeaO4,magnetite, column, it will be noted that there is a very small drop,thus demonstrating that reduction of the magnetite is unnecessary forthe reduction of the nickel and copper oxides and silicates. The columnfor Ni, nickel, illustrates that a Substantial amount of the nickel isremoved from the slag as it goes through the reducer-mixer and that thenickel is lowered to approximately the same level irrespective of theamount of nickel in the ingoing slag. The Cu,

copper, column shows the same trend as the Ni` column. Finally, the Co,cobalt, column shows that the nickel and copper are lowered without anysubstantial lowering of the cobalt content of the slag.

It will be clear to those skilled in this art that the above `examplesare merely by Way of illustration and that the invention readily lendsitself to other useful modifications in practice.

I claim:

1. In the method of treating at least two slags of differing compositionobtained in the production of nickel and copper` by smelting ores ofthose metals, said slags containing a relatively small but valuableamount of nickel and copper in the form of oxides, silicates and suldesand a relatively large amount `of iron compounds mostly in Vthe `form ofVsilicate and relatively small amounts in the form of magnetite andsulfide, one of the slags being relatively high in iron and Vhigh insuldes of copper, nickel and iron in solution in the iron silicate, theother slag being relatively low in iron and low in suldes of copper,nickel and iron in solution in the iron silicate, the improvement whichcomprises passing suldes of copper, nickel and iron held in so-` lution`by the slag high in iron, subjecting the molten slags while undergoingmixing to reduction with a reducing agent at a suitably elevatedtemperature, said reducing agent being employed in `amount suicientselectively to reduce the oxides and silicates of thenickel and copper,converting the reduced nickel and copper into suldes of nickel andcopper with iron sulde, said reducing agent being employed in amountinsuiiicient to reduce a substantial amount of the iron compoundspresent in the slags, permitting the resulting mixture to remainsubstantially quiescent in a settling zone, allowing matte prills tomerge with matte at the bottom of the settling zone, and separating thenal slag from 'the final matte containing the desired nickel andcopper.`

2. Method according to the precedingclaim,

in which the slags are continuously passedV through the reducing andmixing zone while the reducing agent is continuously injected into theslags above the quiescent body of matte, the rate of flow of the slagsand the rate of injection of the reducing agent being regulated toprovide l a detention period for the slags in the reducing and mixingzone suiciently long to permit reduction of the oxides and silicates ofthe nickel and copper but insuiliciently long to permit reduction `ol? asubstantial amount of the iron l compounds present inthe slags, andcontinuously passing the resulting superposed mixture and the underlyingbody of matte from the reducing and mixing and the quiescent zones intoa settling zone.

3. In the method of treating at least two slags of differing compositionobtained in the production of nickel and copper by smelting ores ofthose metals, said slags containing a relatively small but valuableamount of copper, nickel, and cobalt in the form of oxides, silicatesand suliides and a relatively large amount of iron compounds mostly inthe form of silicate and relatively small amounts in the form ofmagnetite and sulfide, one of the slags being relatively high in irronand high in suldes of copper, nickel, cobalt and iron in solution in theiron silicate, the other slagbeing relatively low in iron and low insuliides of copper, nickel, cobalt and 'iron in solution in the ironsilicate, the improvement which comprises passing the slags while molteninto a reducing` and mixing zone, collecting a body of matte in alquiescent zone below the reducing and mixing zone and maintaining thebody of matte in contact with the superposed body of slags to facilitatesettling out of matte prills, mixing the combined molten slags above thequiescent body of matte suiiiciently to salt out a substantial amount ofthe suliides o f copper, nickel, cobalt and iron held in Vsolution bythe slag high in iron,

subjecting the molten slags while undergoing' mixing to reduction with areducing agent at a suitably elevated temperature, said reducing agentbeing employed in amount sufficient selectively to reduce the oxides andsilicates of the copper, nickel and cobalt, converting the reducedcopper, nickel and cobalt into sulfides of copper, nickel and cobaltwith iron sulfide, permitting the resulting mixture to remainsubstantially quiescent in a settling zone, allowing matte prills ofcopper, nickel, cobalt and iron suliides to merge with matte at theyIbottoin of the settling zone, and separating the iinal slag from thefinal matte containing the desired nickel, copper and cobalt.

4. Method according to the preceding claim, in which the slags arecontinuously passed through the reducing and mixing zone while thereducing agent is continuously injected into the slags above thequiescent body of matte, the rate of flow of the slags and the rate ofinjection of Ithe reducing agent being regulated toprovide a detentionperiod for the slags in the reducing and mix'- ing zone sufficientlylong to permit reduction of the oxides and silicates of copper, nickeland cobalt, and continuously ,passing the resulting superposed mixtureand the underlying body of matte from the reducing and mixing and thequiescent zones into a settling zone.

5. In the method of treating slags obtained in the production of nickeland copper by 'smelting ores of those metals, said slags containing arelatively small but valuable amount of nickel and copper in the formVof oxides, silicates and suldes and a relatively large amount of ironcompounds mostly in the form of silicate and relatively small amounts inthe lform of magnetite and sulide,.

the improvement which comprises .passing the slags while molten into areducing and mixing zone, collecting a body of matte in a quiescent zonebelow the reducing and mixing zone and maintaining the body of matte incontact with the superposed body of slags to facilitate settling out vofmatte prills, subjecting the molten slags above the quiescent body ofmatte to reduction 16 Y with a reducing agent while mixing the slags ata suitably elevated temperature, said reducing agent being employed inamount suicient selectively to reduce the oxides and silicates of thenickel and copper, converting the [reduced nickel and copper into suldes.of nickel and copper with the iron suliide present in the slags, saidreducing 'agent being employed in amount insuflicient to reduce asubstantial amount of the iron compounds present in the slags,permitting the resulting mixture to remain substantially quiescent in asettling zone, allowing matte prills of copper, nickel .and iron sulfideto merge with matte at the bottom of the settling zone, and separatingthe Iinal slag from the final matte containing the desired nickel andcopper.

` 6. Method according to claim 5, in which the slags are continuouslypassed through the reducing. and mixing zone while the reducing agent iscontinuously injected into the slags above the quiescent body of matte,the lrate of iiow of the slags and the rate of injection of the reducingagent being regulated to provide a detention period for the slags `inthe reducing and mixing zone suiciently long to permitreduction of theoxides and silicates of the nickel and copper but insufficiently long topermit reduction of a substantial amo-unt of the compounds of iron.

'7. Method according to :claim 5, in which the reducing and mixingactions are obtained by injecting fuel and air into the molten slagsabove the quiescent body of matte. Y

8. Method according to claim 5, in which the Y reducing and mixingactions are obtained by injecting fuel and air intothe molten slagsabove the quiescent body of matte, the slags are continuously passedthrough the reducing and mixing zone while the reducing agent iscontinuously injected into the slags, the rate of flow of the slags andthe rate of injection of the reducing agent being regulated toy provide'a detention period for the slags in the reducing and mixing zonesuniciently long to permit reduction of the oxides and silicates of thenickel and copper but insuiiiciently long to permit reduction of asubstantial amount of the compounds of iron.

9. In the method of treating slags obtained in the production of Ynickeland copper by smelting ores of those metals, said slags containing Aarelatively small but valuable amount of copper, nickel and cobalt in theform of oxides, silicates and suldes and a relatively large amount ofiron compounds mostly in the form of silicate and relatively smallamounts in the form of magnetite and suliide, the improvement whichcomprises passing the slags while molten into a reducing and mixingzone, collecting a body of matte in a quiescent zone below the reducingY, and mixing zone and maintaining the body of.

matte in contact with the superposed body of slags to facilitatesettling out of matte prills, subjecting the .molten slags above thequiescent body of matte to reduction with a reducing agent while mixingthe slags at a suitably elevated temperature, said reducing agent beingemployed in amount sufficient selectively to reduce the oxides andsilicates of the copper, nickel Vand cobalt, converting the reducednickel, copper and cobalt into suldes ci" nickel, copper and cobalt withthe iron suliide present in the slags, permitting the resulting mixtureto remain substantially quiescent in a settling zone, allowing matteprills of copper, nickel, cobalt and iron sulfide to merge with matte atthe bottom of the settling zone, and separating the iinal slag 17 fromthe nal matte containing the desired nickel,

copper and cobalt. y i

10. Method according to the preceding claim, in which i the slags arecontinuously passed through the reducing and mixing zone while thereducing agent is continuously injected into the slagsabove thequiescent body of .matta the rate of flow of the slags and the rate ofinjection of the reducing agent being regulated to provide a detention.period for the slags in the reducing and mixing zone Vsufliciently longto permit reduction of the oxides and silicates of copper, nickel. andcobalt, and continuously passing the resulting superposed mixture andthe underlying body of matte from the reducing and mixing and thequiescent zones into a settling zone. ,l

11. In the method of treating at least two slags of diiering compositionobtained in the production of copper by'smelting copper-bearing ores,said slags containing a relatively small but valuable amount of copperin the form of oxide, silicate and sulde and a relatively large amountof iron compounds mostly in the form of silicate and relatively smallamounts in the form of magnetite and sulfide, one of the-slags beingrelatively high in iron and high in sulfides of copper, and iron insolution in the iron silicate, the other slag being relatively low iniron and low in sulndes of copper and iron in solution in the ironsilicate, the improvement which comprises passing the slags while molteninto a reducing and mixing zone, collecting a body of matte in aquiescent zone below the reducing and mixing zone and maintaining thebody of matte in contact with the superposed body of slags to facilitatesettling out of matte prills, mixing the combined molten slags above thequiescent body of matte suiciently to salt out a substantial amount ofthe suldes of copper and iron held in solution by the slag high in iron,subjecting the molten slags while undergoing mixing to reduction with areducing agent at a suitably elevated temperature, said reducing agentbeing employed in amount sufficient selectively to reduce the oxide andsilicate of the copper, converting the reduced copper into sulfide ofcopper with iron sulfide present in the slags, said reducing agent beingemployed in amount insumcient to reduce a substantial amount of the ironcompounds present in the slags, permitting the resulting mixture toremain substantially quiescent in a settling zone, allowing matte prillsof copper and iron Isulfides to merge with matte at the bottom of thesettling zone, and separating the final slag from the iinal mattecontaining the desired copper.

12. Method according to the preceding claims, in which the slags arecontinuously passed through the reducing and mixing zone while thereducing agent is continuously injected into the slags above thequiescent body of matte, the rate of flow of the slags and the rate ofinjection of the reducing agent being regulated to provide a detentionperiod for the slags in the reducing and mixing zone suiiciently long topermit reduction of the oxide and silicate of the copper butinsufficiently long to permit reduction of a substantial amount of theiron compounds present in the slags, and continuously passing theresulting superposed mixture and the underlying body of matte from thereducing and mixing and the quiescent zones into a settling zone.

13. In the method of treating slags obtained in the production of copperby-smelting copper- 18 bearing ores, said slags containing a relativelysmall but valuable amount of copper in the form of oxide, silicate andsuliide and a relatively large amount of iron compounds mostly in theform of silicate and relatively small amounts in the form of magnetiteand sulfide, the improvement which comprises passing the slags whilemolten into a reducing and mixing zone, collecting a body of matte in aquiescent zone below the reducing and mixing zone and maintaining thebody of matte in contact with the superposed body of slags to facilitatesettling out of matte prills, subjecting the molten slags above thequiescent body of matte toreduction with a reducing agent while mixingthe slags at a suitably elevated temperature,` said reducing agent beingemployed in amount sumcicnt selectively to reduce the oxide and silicateof copper, converting the reduced copper With iron sulde present in theslags into suliide of copper, permitting the resulting mixlture toremain substantially quiescent in a settling zone, allowing matte prillsto merge with matte at the bottom of the settling zone, and separatingthe nal slag from the final matte containing the desired copper.

14. Method according to the preceding claim, in which the slags arecontinuously passed through the reducing and mixing zone while thereducing agent is continuously injected into the slags above thequiescent body of matte, the rate of 'flow of the slags and the rate ofinjection of the reducing agent being regulated to provide a detentionperiod for the slags in the reducing and mixing zone sumciently long topermit reduction of the oxide and silicate of the copper butinsuiciently long to permit reduction of a substantial amount of theiron compounds present in the slags, and continuously passing theresulting superposed mixture and the underlying body of matte froml thereducing and mixing zone into a settling zone.

15. In the method of treating slags obtained in the production or"nickel and copper by smelting ores of those metals, said slagscontaining a relatively small but valuable amount of copper, nickel andcobalt in the form of oxides, silicates and sulfides and a relativelylarge amount oi iron compounds mostly in the form of silicate andrelatively small amounts in the form of magnetite and sulde, theimprovement which comprises passing the slags while molten into areducing and mixing zone, collecting a body of matte in a quiescent zonebelow the reducing and mixing zone and maintaining the body of matte incontact with the superposed body of slags to facilitate settling out ofmatte prills, subjecting the molten slags above the quiescent body ofmatte to reduction with a reducing agent while mixing the slags at asuitably elevated temperature, said reducing vagent being employed inamount sufficient selectively to reduce the oxides and silicates of thecopper `and nickel, converting the reduced copper and nickel With ironsuliide present in the slags into suliides oi copper and nickel, saidreducing agent being insufficient to reduce a substantial amount ofcompounds of cobalt and iron, permitting the resulting mixture to remainsubstantially quiescent in a settling zone, allowing matte prills ofcopper, nickel and iron suldes to merge with matte-at the bottom of thesettling zone, separating the slag from the matte containing the desiredcopper and nickel, subjecting said latter slag containing the cobaltwhile undergoing mixing to reduction at a suitably elevated temperature,the

reducing agent being "employed in amount sufi'ici'ent 'to reduce 'theoxide and silicate of cobalt, converting the reduced cobalt to cobaltsulfide with iron 'sulde lpermitting the resulting `mixture to remainsubstantially quiescent 'in a set- 'tli'n'g 'zei-1e, allowing matteprills of cobalt and iron sulndes to .merge with matte at the bottom ofthe settling zone, `separa'ting the n'al slag from the nal mat-tecontaining the desired cobalt.

1:6. In the method of treating at least two slags of differingcomposition obtained in the production of "nickel and `copper bysmeltin'g 'ores of 'these metals, said slags containing 1a relativelysmall but valuable amount of copper, nickel and cobalt in the "forni 'ofoxides, silicates and sulfl'des land :a relatively large amount of ironcompoundsv mostly `in the `forrnof silicate and relatively smalllamounts in the form 'of magnetite and sulfide, one 'oi the `slags beingrelatively high in iron and high in su-lides of copper, nickel, A'cobaltvand. iron in -solution in the iron silicate, the `other slag lbeingrelatively 4low in iron and loW in suldes Iof copper, nickel, cobalt andiron in solution in the iron silicate, the improvement which comprisespassing the slags while molten Vinto a reduci-ng and mixing zone,collecting 1a lo'ody of matte in a quiescent zone below the reducing andmixing `zone Iand maintaining the body 'of matte in fcontact With4the-superposed body of slags 4to facilita'te rsettling out of matteprills, mixing the lcombined molten slags above the .quiescent body 'ofmatte sufficiently to salt out a substantial amount of the suldes ofcopper, nickel, cobalt and iron lield in solution by the slag high iniron, subjecting the 4molten slags to reduction with 'a reducing agentWhile mixing the slags at a suitably elevated temperature, said reducing-agent being employed in amount s-ui'ci'ent selectively to lreduce theoxides and silicates of the -copper and nickel, converting the reducedlconper and nickel with iron sulfide present in the sla'gs intofsulidesAof copper and nickel, said reducing `agent `being `-insuilicient toreduce a -sublstantial amount of the compounds of cobalt 'and iron,permitting the resulting mixture 'to remain .substantially quiescentVina settling zone, allowing matte prills of copper, nickel and .ironysulfldes to merge with matte at the bottom of the settling none,separating the slag from the matte 'containing the desired lcopper andnickel, subjecting :said lat-ter slag containing the cobalt whileundergoing .mix-ing to reductionat a :suite ably elevated temperature,the reducing agent being employed in amount sucient to reduce the oxideand :silicate of cobalt, converting the reduced cobalt to cobalt suliidewith iron s'ulde, permitting the .resulting mixture .to remain4substantially iquiescent .in a settling zone, :allowing .matte `prillsof cobalt rand iron suldes to Imerge 'with matte at the bottom of thesettling zone, separating the iirral slag from the .iinal mattecontaining the desired cobalt.

1'7. Method according to the preceding claim .in which the slags of'differing composition .are continuously passed through the firstreducing `and mixing zone while the reducing agent is continuouslyinjected into 4the yslags above the quiescent vbody of the matte, therate Aof ow of the slags and .the rate ,of injection of the reducingagent being regulated to ,provide a detention :period .fior the Aslagsin the reducing and mixing zone .suiiiciently long to permit reductionof tire oxides :and :silicates iof the copper and nickel 'butinsun'iciently .long to permit reduction of ia :substantial yamount :ofthe .compounds of vcobalt `and iron, 'and continuously passing theresulting superposeid :mixture 'and the 'underlying bod-y of matte frornthe .reducing and :mixing and the yqtuiescient zones into ea settlingzone.

ANTQN GRONNINGSAETER.

REFERENGES 4clarin) 'The *following references are of record in the ille-of this patent:

UNITED (STATES PATENTS Gronwall July 19, 1932 Patent No. 2,438,911.

Certificate of Correction April 6, 1948. ANTON MARTIN GRONNINGSAETER Itis hereby certified that errors appear in the printed specification ofthe above numbered patent requiring correction as follows: Column 4,line 75, for af read of; column 5, line 74, for the Word suldes readsulfide; column 11, line 27, for hgiher read higher; line 57, for valveread value; column 18, line 40, claim 14, after mixing insert and thequiescent; line 41, same claim, for zone rst occurrence read zones;andthat the said Letters Patent should be read with these correctionstherein that the same may conform to the record of the case in thePatent Office.

Signed and sealed this 17th day of August, A. D. 1948.

THCMAS F. MURPHY,

Am'atant Uommim'oner o/ Patents.

